Performance and noise control for a heat sink air mover

ABSTRACT

A system and method for cooling a heat-generating device. The system comprises a heat sink base for contacting the heat-generating device, and a plurality of heat sink fins extending from the heat sink base, wherein the fins provide airflow passages that are open along a top, a first side and a second side. An ionic air moving device is disposed along at least one side of the heat sink for moving air through the airflow passages, and a fan is mounted adjacent to the top of the fins for moving air through the airflow passages. A controller selectively controls the airflow through the heat sink using only the ionic device, only the fan, or both the ionic device and the fan. A user or a system component may instruct the controller to enter a performance mode, an energy efficiency mode, or an acoustic mode.

BACKGROUND

1. Field of the Invention

The present invention relates to heat sinks having an air mover, and methods of controlling the air mover of a heat sink.

2. Background of the Related Art

Computer systems include numerous components that use electrical energy and produce heat as a byproduct. Typically, these components are organized in a housing or chassis for efficient placement, storage and operation. In large computer systems, these individual chassis may be further organized into a rack-based computer system that enables many rack-mounted components to be operated in a high-density arrangement, which can produce a considerable amount of heat. However, each individual chassis may have its own unique cooling requirements that may change over time with varying workload.

Heat produced by the components within the chassis must be removed to control internal component temperatures and to maintain system reliability, performance, and longevity. In a conventional rack-based computer system, rack-mounted fans move cool air through the rack to cool the components. Standalone chassis may have their own dedicated fans. However, air moving through the chassis will tend to take the path of least resistance and it becomes necessary to consider air flow impedance between and among components and groups of components within a chassis. In order to achieve adequate airflow to each component without excessive operation of the fans, system designers will position and orient components within the chassis with due consideration to the need for adequate airflow.

A processor can produce a great deal of heat during heavy usage and is typically secured to a motherboard in direct thermal communication with large heat sink. The heat sink fins extend away from the motherboard into the path of airflow through the chassis and generally comprise a group of fins that are oriented parallel to the airflow direction. Similarly, a chassis may also support multiple memory modules that are commonly arranged together on a motherboard and oriented parallel to the airflow direction through the chassis. However, each and every processor, memory module, and other component within the chassis need adequate airflow.

In any given chassis design, the component layout and operation may be tested to assure adequate airflow to each component. Still, there is a desire to avoid excessive use of fans, since fan operation can consume significant power and produce significant noise. It is desirable, therefore, to use airflow efficiently and effectively. This objective is complicated by the dynamic nature of workloads, and thus heat production, among the chassis components.

BRIEF SUMMARY

One embodiment of the invention provides a system for cooling a heat-generating device. The system comprises a heat sink base for contacting the heat-generating device, and a plurality of heat sink fins extending from the heat sink base, wherein the fins provide airflow passages that are open along a top, a first side and a second side. An ionic device is disposed along at least one side of the heat sink for moving air through the airflow passages, and a fan is mounted adjacent to the top of the fins for moving air through the airflow passages. A controller is configured to selectively control the airflow through the heat sink using only the ionic device, only the fan, or both the ionic device and the fan.

Another embodiment of the present invention provides a method of cooling a heat-generating device. The method comprises inducing airflow through a heat sink from a first side of the heat sink to a second side of the heat sink using an ionic device, wherein the heat sink has a base in thermal communication with the heat-generating device and a plurality of heat sink fins extending from the heat sink base, wherein the fins provide airflow passages that are open along a top and between the first and second sides. The method further comprises inducing airflow through the top of the heat sink using a fan. Still further, the method selectively controls the airflow using only the ionic device, only the fan, or both the ionic device and the fan.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a heat sink with a fan and an ionic air moving device.

FIG. 2 is a perspective view of the heat sink with the fan and the ionic air moving device secured to the heat sink.

FIG. 3 is a top view of the heat sink with the fan removed to show the positioning of an array of emitter electrodes along a first end of the heat sink.

FIG. 4 is a top view of the cut-out region of FIG. 3 showing the positioning of each emitter electrode with respect to the heat sink fins.

FIG. 5 is a block diagram of a system for cooling a processor in accordance with one embodiment of the invention.

FIGS. 6A-6C are block diagrams of alternative configurations of a cooling system including a heat sink, a fan, and at least one set of emitter electrodes.

FIGS. 7A-7B are block diagrams of cooling systems that include ionic air moving devices that have an independent set of collector electrodes, rather than using the heat sink fins as the collector electrodes.

DETAILED DESCRIPTION

One embodiment of the present invention provides a system for cooling a heat-generating device. The system comprises a heat sink base for contacting the heat-generating device, and a plurality of heat sink fins extending from the heat sink base, wherein the fins provide airflow passages that are open along a top, a first side and a second side. An ionic air moving device is disposed along at least one side of the heat sink for moving air through the airflow passages, and a fan is mounted adjacent to the top of the fins for moving air through the airflow passages. A controller is configured to selectively control the airflow through the heat sink using only the ionic air moving device, only the fan, or both the ionic air moving device and the fan.

While advances have been made in the amount of power that can be cooled using an ionic air moving device, the present systems and methods augment the ionic air moving device with one or more conventional air moving devices, such as a fan, for the higher power applications. A top mounted impingement fan allows for unrestricted side to side and/or front to back airflow through the heat sink provided by the ionic devices. The ionic device are thus able provide the airflow sufficient to cool a heat-generating device up to certain limits. For example, where the heat-generating device is a processor, the ionic air moving device may provide sufficient airflow to cool the processor until the processor power consumption is about 70 W. Above about 70 W power consumption, the fan can replace or augment this airflow at higher rates of airflow.

The heat sink includes either fins, pins or other structures having a high surface area for transferring heat into air that is made to flow over the surfaces. Furthermore, the fins, pins or other structures generally extend from the heat sink base, which contacts, or is otherwise in thermal communication with, a heat generating components. The fins, pins or other structures may be supplemented with heat spreaders or heat pipes.

In preferred embodiments, the fan is an impingement fan disposed along the top of the heat sink. In a first configuration, the fan pushes air into the airflow passages from the top of the fins and the air exits the airflow passages at the first and second sides. In a second configuration, the fan draws the air out of the airflow passages at the top of the fins and air enters the airflow passages at the first and second sides.

In one embodiment, the system further comprises a temperature sensor that is coupled to the heat sink base. The temperature sensor provides a temperature signal to the controller for use in controlling the operation of the ionic device and the fan. Optionally, the controller may be implemented as a control circuit that is dedicated to the operation of the fan and ionic device. Such an embodiment is mostly self-contained and only requires an external source of electrical power.

In certain embodiments, the heat-generating device is a processor. For example, the processor and the heat sink may be provided on an expansion card. Alternatively, the processor may be installed on a motherboard and the controller is a service processor for the motherboard. In the later alternative, the service processor may be, without limitation, selected from a baseboard management processor and an integrated management module.

The ionic air moving device may be configured to induce airflow through the plurality of airflow passages in the heat sink. For example, the ionic air moving device may comprise a plurality of electrode pairs, where each electrode pair includes an ion emitter electrode disposed a spaced distance upstream in the airflow direction from a collector electrode. The emitter electrode and the collector electrode are coupled to a power source for applying an electrical potential between the emitter electrode and the collector electrode. The controller may control the electrical potential between the emitter and collector electrode of each electrode pair to affect the desired rate of airflow and cooling. A couple of primary advantages of using an ionic air moving device are that it operates silently and has no moving parts.

In one embodiment, the plurality of electrode pairs are aligned with the airflow passages through the heat sink. In one configuration, the emitter electrode may be a thin wire, and the ion collector electrode may be a portion of the heat sink fins. In an alternative configuration, the emitter electrode may be a needle. A high electric potential, such as 8000V DC or greater, is applied across the two electrodes leading to ionization of air around the wires. The ions are then attracted to the ion collector electrode and, in the process, transfer momentum to the adjacent air molecules resulting in airflow in a direction from the emitter electrode to the collector electrode.

Where a nonionic air moving device has already established an airflow rate through the chassis in an airflow direction, the ionic movement of air may serve to enhance the airflow rate so long as the ion emitter electrode is upstream of the collector electrode (to cause airflow enhancement or reduce airflow impedance). It should be recognized that all references to upstream or downstream positions are made with reference to the desired airflow direction. It is also within the scope of the invention to provide more than one ionic air moving device, such as one ionic air moving device at each end of the heat sink to force air inwardly from each end and out through the top of the heat sink. Accordingly, if the fan is mounted to the top of the heat sink and directed to draw air out of the heat sink air passages, then the fan and the ionic air moving devices may induce airflow in the same direction. In another alternative, an ionic air moving device could be positioned at one end and the fan could be positioned at the same end or the opposite end to direct airflow in the same direction as the ionic air moving device.

More generally, ionic air moving devices for use in the present invention may comprise a high curvature electrode for emitting ions, such as the tip of a needle or a thin wire, and a blunt electrode for collecting ions, such as a plate or a ring. Although the electrical potential is preferably 8000V DC or greater, the power input to the ionic device may be less than 20 W with the proper optimization.

Another embodiment of the present invention provides a method of cooling a heat-generating device. The method comprises inducing airflow through a heat sink from a first side of the heat sink to a second side of the heat sink using an ionic device, wherein the heat sink has a base in thermal communication with the heat-generating device and a plurality of heat sink fins extending from the heat sink base, wherein the fins provide airflow passages that are open along a top and between the first and second sides. The method further comprises inducing airflow through the top of the heat sink using a fan. Still further, the method selectively controls the airflow using only the ionic device, only the fan, or both the ionic device and the fan.

Certain optional embodiments of the method may include two or more modes of operating the air movers (i.e., the ionic device and the fan). For example, the controller may operate the air movers in a performance mode, an energy efficiency mode or an acoustic mode. While the controller will operate the air movers in only one mode at a time, the controller may be placed in two or more of these modes at different times in accordance with input received from a user or another system component or controller, such as a service processor.

For example, in response to input received from a user or system controller selecting a performance mode, the controller induces airflow through the heat sink using only the fan. In performance mode, it is the performance of the heat-generating device that is given the greatest priority. The fan is able to produce higher airflow rates than the ionic air moving device, so the fan is used to control the temperature of the heat-generating despite a high level of performance. Where the heat-generating device is a processor, a high level of performance may be a high workload or high processor speeds that result in greater heat generation. The high volume of airflow induced by the fan allows the processor to continue operation at these high levels of performance without the need to throttle the processor.

In response to input received from a user or system controller selecting an energy efficiency mode, the controller induces airflow through the heat sink using the ionic device up to a setpoint condition and using the fan above the setpoint condition. Optionally, the setpoint condition is selected from a temperature setpoint, an energy setpoint, or a combination thereof. When the heat generating device is a processor, the temperature setpoint may be a processor temperature setpoint, and the energy setpoint may be a processor energy consumption setpoint. In accordance with the energy efficiency mode, the system starts out using only the ionic air moving device in order to get the best cooling efficiency. If the workload of the CPU is fluctuates or increases, then the fan can be triggered by a temperature or energy threshold to augment the cooling.

In response to input received from a user or system controller selecting an acoustic mode, the controller induces airflow through the heat sink using only the ionic device. It should be recognized that if the heat-generating device produces enough heat, as with a processor under a heavy workload, then the maximum airflow capacity of the ionic device may be insufficient to cool the heat-generating device. However, in the acoustic mode, in response to the processor reaching a temperature exceeding a processor temperature setpoint, airflow through the heat sink continues to be provided only by the ionic device, even if this results in throttling a processor speed. The use of only the ionic air moving device maintains silent operation to minimize acoustic levels.

FIG. 1 is an exploded perspective view of a cooling system 10 including a heat sink 20 with a fan 30 and an ionic air moving device 40. The heat sink 20 is shown as a conventional heat sink having a base 22 and a plurality of fins 24. The base 22 is secured in thermal communication with a heat-generating device (not shown), and the plurality of fins 24 forms a plurality of airflow passages therebetween. Specifically, the heat sink 20 has ten (10) fins 24 and forms nine (9) airflow passages that are open along the top 26 and open at a first end 27 and a second end 28. The fan 30 is secured over the top 26 of the heat sink fins 24 and may be directed to blow air upward or downward. A frame 42 secures a plurality of emitter electrodes 44 and couples them to a negative (−) terminal of a voltage source. The heat sink 20 is coupled to a positive (+) terminal of a voltage source, such that the individual fins 24 serve as collector electrodes. The electrical potential applied between the emitter electrodes 44 and the fins 24 cause a flow of ions from the emitter electrodes 44 to the fins 24. The flow of ions causes a flow of air in the same direction. Preferably, the frame 42 and the emitter electrodes 44 are secured along one of the open sides 27 of the heat sink 20 to induce airflow through the plurality of air passages between the plurality of fins. Accordingly, the ionic air moving device 40 generates airflow from the first side 27 to the second side 28 of the heat sink.

FIG. 2 is a perspective view of the cooling system 10 with the fan 30 secured to the top 26 of the heat sink 20 and the frame 42 secured to the first side 27 of the heat sink 20. The system 10 is shown with the fan 30 operating to draw air out through the top 26 of the heat sink 20 from the plurality of air passages. The airflow flows into the open first side 27 and the open second side 28, then across the surfaces of the fins 24 absorbing heat before being exhausted from the heat sink 20 through the fan 30. Although the emitter electrodes 44 are shown in their operable position, the emitter electrodes are not being used in FIG. 2 to induce airflow. The emitter electrodes are made from thin wire and do not cause any appreciable resistance to the airflow generated by the fan 30. More about the operation of the ionic air moving device 40 will be discussed in regard to FIG. 3.

FIG. 3 is a top view of the heat sink 10 with the fan removed to show the positioning of an array of emitter electrodes 44 in a frame 42 along the first end 27 of the heat sink 20. The emitter electrodes 44 are electrically coupled to a negative terminal of a power supply/voltage regulator, and the heat sink fins 24 are electronically coupled to a positive terminal of the power supply/voltage regulator. As shown, the emitter electrodes 44 are in the form of wires that run parallel to the leading edge of the fins 24. The emitter electrodes 44 are shown centered between a pair of adjacent fins, but may be aligned with the fins or otherwise positioned. A cut-out region of FIG. 3 is shown in greater detail in FIG. 4.

FIG. 4 is a top view of the cut-out region of FIG. 3 showing the positioning of each emitter electrode 44 with respect to a leading edge 29 of the heat sink fins 24. The frame 42 secures the wires that form the emitter electrodes 44 in a spaced-apart relationship to each other. Preferably, the pitch between adjacent emitter electrodes 44 (distance X) is the same as the pitch between adjacent fins 24 (also distance X). The frame 42 may also be used to establish a spaced-apart relationship between the emitter electrodes 44 and the first end 27 of the heatsink 20 (distance Y). The wavy arrows in FIG. 4 indicate the airflow generated by use of the ionic air moving device 40.

As shown, the emitter electrodes 44 have a negative charge that allows negatively charged ions to form. The electrical potential between the emitter electrodes 44 and the fins 24 induces the ions to move through air from the emitter electrodes 44 to the fins 24, which form the collector electrodes. This movement of ions (shown by wavy arrows in FIG. 4) drags air with it to cause airflow into the open first end 27 of the heatsink and out the open second end 28 (See FIG. 3) of the heat sink.

FIG. 5 is a block diagram of a system 50 for cooling a processor 52 in accordance with one embodiment of the invention. The system 50 includes the system 10 of FIGS. 1 through 4, which comprises the heat sink 20, the fan 30, and the emitter electrodes 44. The base of the heatsink 20 is in thermal communication with the processor 52 to conduct heat away from the processor to the plurality of heat sink fins.

A controller 54 receives a temperature signal from a temperature sensor 56 that measures, in various embodiments, either the temperature of the heatsink base, the temperature of the processor 52, or the temperature of some related component. Accordingly, the temperature sensor 56 may be coupled to the heat sink or the processor, but may also be a temperature sensor that is an internal element of the processor. Where the temperature sensor is coupled directly to the heat sink, the temperature signal may be communicated to the control as an analog signal requiring an analog-to-digital conversion. Where the temperature sensor is internal to the processor, the temperature signal produced by the processor will already be a digital signal that may be communicated, for example, via a communications bus with the controller. Where the controller 54 is a baseboard management controller (BMC) or an integrated management module (IMM), the communications bus may be an inter-integrated circuit (I2C) bus.

The controller 54 is in electronic communication with both the fan 30 and the ionic air moving device 40 and controls the operation of both devices. As for the ionic air moving device 40, the controller 54 may provide a control signal to a power supply/voltage regulator 58 to turn the device 40 on or off, or perhaps also indicate a desired voltage to be applied between the positive and negative terminals of the regulator 58. Because the emitter electrodes 44 are coupled to the negative terminal and the fins of the heat sink 20 are coupled to the positive terminal, the electrical potential causes a flow of ions that lead to airflow through the heat sink 20.

The controller 54 receives input from either a user interface 60 or another system component 62, such as a remote management module or system that manages the energy and acoustic policies for a datacenter. As described herein, the controller 54 may establish a plurality of operating modes, such as a performance mode, an energy efficiency mode, and an acoustic mode. For example, in response to input received from the user interface or other system component selecting the performance mode, the controller induces airflow through the heat sink using only the fan. In response to input received from the user interface or other system component selecting an energy efficiency mode, the controller induces airflow through the heat sink using the ionic device up to a setpoint condition and using the fan above the setpoint condition. Optionally, the setpoint condition is selected from a temperature setpoint, an energy setpoint, or a combination thereof. When the heat generating device is a processor, the temperature setpoint may be a processor temperature setpoint, and the energy setpoint may be a processor energy consumption setpoint. In accordance with the energy efficiency mode, the system starts out using only the ionic air moving device in order to get the best cooling efficiency. If the workload of the CPU is fluctuates or increases, then the fan can be triggered by a temperature or energy threshold to augment the cooling. In response to input received from the user interface or other system component selecting an acoustic mode, the controller induces airflow through the heat sink using only the ionic device. It should be recognized that if the heat-generating device produces enough heat, as with a processor under a heavy workload, then the maximum airflow capacity of the ionic device may be insufficient to cool the heat-generating device. However, in the acoustic mode, in response to the processor reaching a temperature exceeding a processor temperature setpoint, airflow through the heat sink continues to be provided only by the ionic device, even if this results in throttling a processor speed. The use of only the ionic air moving device maintains silent operation to minimize acoustic levels.

FIGS. 6A-6C are block diagrams of alternative configurations of a cooling system including a heat sink 20, a fan 30, and at least one set of emitter electrodes 44. In FIG. 6A, a fan 30 is positioned at the same end of the heat sink 20 as a set of emitter electrodes 44, preferably with the fan directing airflow in the same direction as the ionic air moving device, which includes the emitter electrodes and the heat sink. FIG. 6B is similar to FIG. 6A, except that the fan 30 is positioned on the opposite end of the heat sink 20 from the emitter electrodes 44. Still, it is preferable that the fan direct airflow in the same direction as the ionic air moving device formed by the emitter electrodes and the heat sink. In FIG. 6C, a set of emitter electrodes 44 is positioned at each end of the heat sink 20 to force air inwardly from each end and out through the top of the heat sink. The fan 30 is mounted to the top of the heat sink and is directed to draw air out of the heat sink air passages. Accordingly, the fan induces airflow in the same general direction or path as the two ionic air moving devices.

FIGS. 7A-7B are block diagrams showing further embodiments in which the ionic air moving device includes an independent set of collector electrodes 70, rather than using the heat sink fins as the collector electrodes. The ionically induced airflow still flows from emitter electrodes 44 to collector electrodes 70, such that airflow can be induced through the heat sink 20. The dashed boxes represent the alternative placements of a fan. In FIG. 7A, the arrangement of the emitter electrodes 44 and collector electrodes 70 causes airflow that is directed into one end of the heat sink 20. By contrast, the arrangement of the emitter electrodes 44 and collector electrodes 70 in FIG. 7B allows the ionic air moving device to draw airflow out of the end of the heat sink 20. It should be recognized that any of the embodiments described above may utilize collector electrodes that are separate from the heat sink to achieve the same general airflow as described in relation to those embodiments where the heat sink fins served as the collector electrodes.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components and/or groups, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. 

What is claimed is:
 1. A system for cooling a heat-generating device, comprising: a heat sink base for contacting the heat-generating device; a plurality of heat sink fins extending from the heat sink base, wherein the fins provide airflow passages that are open along a top, a first side and a second side; an ionic device disposed along at least one side of the heat sink for moving air through the airflow passages; a fan mounted adjacent to the distal end of the fins for moving air through the airflow passages; and a controller configured to selectively control the airflow through the heat sink using only the ionic device, only the fan, or both the ionic device and the fan.
 2. The system of claim 1, wherein the fan is disposed along the top of the heat sink.
 3. The system of claim 2, wherein the fan pushes air into the airflow passages from the top of the fins and the air exits the airflow passages at the first and second sides.
 4. The system of claim 1, wherein the fan draws the air out of the airflow passages at the top of the fins and air enters the airflow passages at the first and second sides.
 5. The system of claim 1, further comprising: a temperature sensor coupled to the heat sink base, wherein the temperature sensor provides a temperature signal to the controller.
 6. The system of claim 5, wherein the controller includes a control circuit dedicated to the operation of the fan and ionic device.
 7. The system of claim 1, wherein the heat-generating device is a processor.
 8. The system of claim 7, wherein the processor and the heat sink are provided on an expansion card.
 9. The system of claim 7, wherein the controller is a service processor in communication with the processor.
 10. The system of claim 9, wherein the service processor is selected from a baseboard management processor and an integrated management module.
 11. A method of cooling a heat-generating device, comprising: inducing airflow through a heat sink from a first side of the heat sink to a second side of the heat sink using an ionic device, wherein the heat sink has a base in thermal communication with the heat-generating device and a plurality of heat sink fins extending from the heat sink base, wherein the fins provide airflow passages that are open along a top and between the first and second sides; inducing airflow through the top of the heat sink using a fan; and selectively controlling the airflow using only the ionic device, only the fan, or both the ionic device and the fan.
 12. The method of claim 11, further comprising: in response to input received from a user or system controller selecting a performance mode, inducing airflow through the heat sink using only the fan.
 13. The method of claim 11, further comprising: in response to input received from a user or system controller selecting an energy efficiency mode, inducing airflow through the heat sink using the ionic device up to a setpoint condition and using the fan above the setpoint condition.
 14. The method of claim 13, wherein the setpoint condition is selected from a temperature setpoint, an energy setpoint, or a combination thereof.
 15. The method of claim 14, wherein the heat generating device is a processor, the temperature setpoint is a processor temperature setpoint, and the energy setpoint is a processor energy consumption setpoint.
 16. The method of claim 11, further comprising: in response to input received from a user or system controller selecting an acoustic mode, inducing airflow through the heat sink using only the ionic device.
 17. The method of claim 16, wherein the heat-generating device is a processor.
 18. The method of claim 17, further comprising: in response to the processor reaching a temperature exceeding a processor temperature setpoint while in the acoustic mode, continuing to induce airflow through the heat sink using only the ionic device and throttling a processor speed.
 19. The method of claim 11, wherein the fan induces airflow into the heat sink through the top of the heat sink and out the first and second sides of the heat sink.
 20. The method of claim 11, wherein the fan induces airflow into the heat sink through the first and second sides of the heat sink and out the top of the heat sink. 